Water flooding is a conventional method of enhancing oil recovery for reservoirs. In this method, water is injected into underground formation through injection wells and oil or other hydrocarbon is driven by the water toward and produced in production wells. When water flows into pores of the media in the formation occupied by the oil, clays and other formation fines are released and flowed with the injection water. The released formation particles may accumulate and plug the pore throats in the flow channels, which causes lower water sweep efficiency and reduced oil recovery.
Normally, these fines, including the clays, are quiescent, causing no obstruction of flow to the wellbore via the capillary system of the formation. However, when the fines are disturbed, they begin to migrate in the production stream and, too frequently, they encounter a constriction in the capillary where they bridge off and severely diminish the flow rate.
A phenomenon that disturbs the quiescent clays and fines is often the introduction of water foreign to the formation. The foreign water is often fresh or relatively fresh water compared to the native formation brine. As noted, the water is frequently intentionally introduced such as for purposes of water flooding.
Sometimes the loss of permeability is due to clay swelling with relatively fresh water without migration of the clay particles, although, often clay swelling is accompanied by migration of clays and fines. Sometimes non-swelling clays can respond to the foreign water and begin to migrate. It is believed that swelling clays are the major mechanism of fines migration and/or swelling, because when formation cores are analyzed, the presence of swelling clays are an excellent indicator that the formation will be sensitive to foreign water intrusion, while the presence of non-swelling clays only is inconclusive.
Generally, swelling clays are in the smectic group including clay minerals such as montmorillonite, beidellite, nontronite, saponite, hectorite, and sauconite. Of these, montmorillonite is the clay mineral found most commonly in formation core analysis. Montmorillonite is commonly associated with clay minerals known as mixed-layer clays.
Migrating fines include a host of clay and other minerals in minute particle size, for example, feldspars, fine silica, kaolinite, allophane, biotite, talc, illite, chlorite and the swelling clays themselves. Further information is found in U.S. Pat. No. 5,160,642, incorporated by reference herein in its entirety.
Clays can also cause trouble in areas other than permeability reduction. When they are a component in shales, sandstones, or other formations, contact with a foreign water or at times with any water can cause the formation to lose strength or even disintegrate. This is a problem in building foundations, road beds, drilling wells, enhanced oil recovery and any situation where the formation strength is important.
There have been numerous attempts to control the ill effects of water on clay and/or other fines. These efforts have been principally in the oil exploration and production industry. One idea is to convert the clay from the swelling sodium form or the more rare swelling lithium form to another cation form which does not swell as much.
In other approaches, a number of materials have been used as sacrificial materials to plate or coat the clays and protect them from the degradation caused by contact with water and caustic which is often used in the water flood material. A surface active agent is often included with the water in secondary production and well treatment. When such surfactants are used, they often adhere to the clay surfaces and build up a plurality of layers, thus being effectively removed from the water flood material and lost, causing an economic disadvantage requiring more surfactant to be added to the subsurface formation than would be necessary. Sugars have also been used as sacrificial materials for nonionic surfactants to coat, or plate, on clay and sand particles by hydrogen bonding to the oxide surfaces. However, since the —OH group is polar, the sugars tend to layer up on the oxide surfaces. Furthermore, the sugars alone do not effectively plate or coat the edges of the clay platelets, so that complete protection of the clays is not obtained.
Accordingly, it would be desirable to provide a composition and method that would provide a high degree of stabilization and control of fines migration, particularly those in subterranean formations.